Two-dimensional metal-organic layers (MOLs) from alternatively connected benzene-tribenzoate ligands and Zr₆(μ₃-O)₄(μ₃-OH)₄ or Hf₆(μ₃-O)₄(μ₃-OH)₄ secondary building units can be prepared in gram scale via solvothermal synthesis. However, the reason why the monolayers did not pack to form thick crystals is unknown. Here we investigated the surface structure of the MOLs by a combination of sum-frequency generation spectroscopy, nanoscale infrared microscopy, atomic force microscopy, aberration-corrected transmission electron microscopy, and compositional analysis. We found a partial coverage of the monolayer surface by dangling tricarboxylate ligands, which prevent packing of the monolayers. This finding illustrates low-density surface modification as a strategy to prepare new two-dimensional materials with a high percentage of exposed surface.

中文翻译：

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在二维金属有机层上探测表面结构以了解抑制的层间堆积

从择一地连接苯三苯甲酸酯配体和Zr二维金属-有机层（摩尔）₆（μ ₃ -O）₄（μ ₃ -OH）₄或Hf ₆（μ ₃ -O）₄（μ ₃ -OH）₄二级建筑单元可以通过溶剂热合成以克为单位制备。但是，单层不堆积形成厚晶体的原因尚不清楚。在这里，我们通过和频产生光谱，纳米级红外显微镜，原子力显微镜，像差校正透射电子显微镜和成分分析相结合的方法研究了MOL的表面结构。我们发现悬垂的三羧酸酯配体可部分覆盖单层表面，从而防止单层堆积。这一发现表明，低密度表面改性是制备具有高暴露表面百分比的新型二维材料的一种策略。